1. Field of the Invention
The present invention relates generally to methods and apparatus for the endoluminal placement of tubular prostheses, such as grafts, stents, and other structures. More particularly, the present invention relates to the implantation of luminal prostheses in a sealing layer within a body lumen.
Vascular aneurysms are the result of abnormal dilation of a blood vessel, usually resulting from disease and/or genetic predisposition which can weaken the arterial wall and allow it to expand. While aneurysms can occur in any blood vessel, most occur in the aorta and peripheral arteries, with the majority of aortic aneurysms occurring in the abdominal aorta, usually beginning below the renal arteries and often extending distally into one or both of the iliac arteries.
Aortic aneurysms are most commonly treated in open surgical procedures where the diseased vessel segment is bypassed and repaired with an artificial vascular graft. While considered to be an effective surgical technique, particularly considering the alternative of a usually fatal ruptured abdominal aortic aneurysm, conventional vascular graft surgery suffers from a number of disadvantages. The surgical procedure is complex and requires experienced surgeons and well-equipped surgical facilities. Even with the best surgeons and equipment, however, the patients being treated frequently are elderly and weakened from cardiovascular and other diseases, reducing the number of eligible patients. Even for eligible patients, conventional aneurysm repair surgery performed prior to rupture has a relatively high mortality rate, usually from 2% to 10%. Morbidity related to the conventional surgery includes myocardial infarction, renal failure, impotence, paralysis, and other conditions. Additionally, even with successful surgery, recovery can take several weeks and often requires a lengthy hospital stay.
In order to overcome some or all of these drawbacks, endovascular graft placement procedures for the treatment of aneurysms have been proposed. Generally, such endovascular procedures will deliver a radially compressed graft intravascularly to the aneurysm. The graft is then expanded in situ, either by releasing a self-expanding graft or by internally expanding a malleable graft (e.g. using a balloon catheter) to protect the aneurysm. Usually, the vascular graft will comprise both a frame and a liner, where the frame provides the necessary mechanical support and the liner provides the necessary blood barrier.
While highly promising, the endovascular placement of vascular grafts is problematic in several respects. In contrast to surgically implanted grafts, which are sutured in place, endovascularly placed grafts can be difficult to anchor and position. Reliance on the outward spring-force of a self-expanding graft is not always sufficient. Malleable grafts, in contrast, may be easier to initially anchor but may be less able to expand and contract with the blood vessel during the continuous pulse of the patient. While the use of hooks or barbs for anchoring grafts into the blood vessel wall has been proposed, such devices can be traumatic and can loosen from the blood vessel wall over time. As the anchoring of the vascular prosthesis loosens over time, blood can begin to bypass the graft and flow into the region between the graft and the blood vessel wall. Such misdirected blood flow into the aneurysm can again expose the patient to risk of aneurysm rupture and its consequences. Additionally, heretofore, it has been difficult to radially reinforce both self-expanding and malleable graft structures to help in maintaining the structures within the blood vessel.
Referring to Prior Art FIGS. 1-3, the problem of blood flow leakage past a graft structure 10 implanted within the region of an aneurysm A in a blood vessel BV is illustrated. While the graft 10 may be adequately anchored on each side of the aneurysm A, as illustrated in FIG. 1, over time the inner surface of the blood vessel lumen can partially separate from the outer surface of the graft 10, as illustrated in FIGS. 2 and 3. Such separations S can allow bypass blood flow into the region of the aneurysm A.
For these reasons, it would be desirable to provide improved luminal prostheses and methods for their implantation which can overcome at least some of the difficulties described above. In particular, it would be desirable to provide intraluminal prostheses and methods for their implantation which would provide a generally fluid tight seal circumscribing at least one end of the prosthesis, and preferably both ends or the entire length of the prosthesis, to prevent bypass blood or other fluid flow into the interstitial region between the inner wall of the body lumen and the outer surface of the prosthesis. In particular, it would be desirable if such improved prostheses and methods for their implantation would provide for sealing of the prosthesis which would resist separating from the intraluminal wall in order to prevent such bypass flow in a long-term or permanent fashion after implantation of the prosthesis. In some cases, it will be desirable to provide methods which permit such sealing implantation when using otherwise conventional prosthesis structures, such as vascular stents and grafts. In other cases, it will be desirable to provide improved prosthesis structures which incorporate features which provide for such sealing implantation when implanted using methods according to present invention.
2. Description of the Background Art
The delivery of polymerizable fluids to body tissues for a variety of purposes, including xe2x80x9cpavingxe2x80x9d of vascular lumens, has been proposed. See, for example, PCT Publications WO 94/24962 and WO 94/21324, and U.S. Pat. No. 5,092,841. Luminal prostheses which are delivered in a compliant state and hardened in situ by exposure to heat, radiation, or other polymerization-initiating event are described in U.S. Pat. Nos. 5,344,444; 5,334,201; and 5,100,429; EP 521573; and de Vries et al., xe2x80x9cInstant Tubular Prosthesis: A Totally New Concept,xe2x80x9d International Congress VII Endovascular Interventions, Phoenix, Arizona, February 1994. A fabric prosthesis which is secured to an inner vascular wall by a contact adhesive, such as cyanoacrylate, is described in U.S. Pat. No. 4,577,631. The use of autologous fibrin glue for sealing porous, fabric grafts prior to open surgical implantation is described in Kjaergard and Weis-Fogh (1994) Card. Surg. 2:45-46. A tubular prosthesis having an annular cavity for receiving a plastic material to enlarge and anchor the prosthesis within a blood vessel is described in U.S. Pat. No. 5,156,620. A tubular prosthesis having inflatable cuffs on each end is described in U.S. Pat. No. 3,991,767. A tubular prosthesis having everted cuffs for receiving sutures is described in U.S. Pat. No. 4,728,328. A tubular stent having hook-like projections over its outer surface is described in U.S. Pat. No. 5,167,614. A tubular stent having a plurality of self-locking fingers extending outward from its outer surface is described in U.S. Pat. No. 5,344,426. A fluid delivery catheter comprising concentric lumens in a balloon structure is described in U.S. Pat. No. 5,295,962. A vascular prosthesis comprising two porous concentrically associated tubes with a helical spring enclosed therebetween is disclosed in U.S. Pat. No. 4,130,904. A vascular prosthesis comprising a multilaminar tubular member is disclosed in U.S. Pat. No. 5,354,329. Microporous materials suitable for the fabrication of prosthetic devices are described in U.S. Pat. Nos. 3,890,107 and 5,348,788.
The present invention provides methods and apparatus for the transluminal positioning of tubular prostheses at a target location within a body lumen. The tubular prostheses are suitable for a wide variety of therapeutic uses, including stenting of the ureter, urethra, biliary tract, and the like. The devices and methods will also find use in the creation of temporary or long-term lumens, such as the formation of fistulas. The present invention will find its greatest use, however, in the placement of endovascular grafts into blood vessels for the treatment of abdominal and other aneurysms, vascular stenoses, and the like.
According to the method of the present invention, a tubular prosthesis is delivered to the target site within the body lumen in a radially compressed configuration and is expanded in situ at the target location so that an exterior surface of the prosthesis engages an inner wall of the body lumen over an interface region therebetween. Radial expansion of the prosthesis may be effected in any conventional manner, including the use of a balloon catheter for expanding malleable prostheses, the release of compressed, self-expanding prostheses from suitable delivery catheters, and the like. The present invention particularly provides for expansion of the prostheses into a sealing layer which is disposed in or over at least a portion of the interface region.
The sealing layer may be disposed within substantially the entire interface region, or may be disposed over one or more discrete, circumferential bands within the interface region. Usually, the sealing layer will be disposed at least at each end of the tubular prosthesis in order to provide a barrier against the bypass leakage of fluid into portions of the interface region therebetween. Preferably, the sealing layer will occupy substantially the entire interface region.
The sealing layer may be composed of virtually any material which is biocompatable and capable of conforming to the interface region between the outer wall of the tubular prosthesis and the inner wall of the body lumen. Exemplary materials include gels, foams, adhesives, biological polymers, compliant sleeves, sponges, porous matrices and meshes, and the like. In some cases, the materials are initially present on the prosthesis or delivered in a fluid or semi-solid state to the interface region, and thereafter cured or hardened to achieve the final, desired geometry. Additionally, the sealing layer may be composed of materials which expand in situ in order to fully conform to the geometry of the interface region, e.g. including materials such as hydrophilic gels, hydrophilic foams, and the like. An exemplary material for the sealing layer comprises a microporous mesh, particularly composed of silicone rubber and similar materials.
In a first particular aspect of the present invention, the sealing layer may be initially formed or disposed over at least a portion of the exterior surface of the tubular prosthesis prior to in situ expansion. In such cases, the tubular prosthesis will usually be pre-coated or covered with the material of the sealing layer prior to introduction of the prosthesis to the body lumen.
In a second particular aspect of the method of the present invention, the material of the sealing layer may be introduced in an initial step prior to introduction of the tubular prosthesis. Usually, a fluid delivery catheter will be employed to apply the sealing layer material in a fluid or semi-solid state over at least a portion of the interface region. The fluid delivery catheter is removed, and a prosthesis delivery catheter is then introduced to the target location. The prosthesis carried by the catheter may then be expanded in situ so that it engages and conforms to the material of the sealing layer.
Apparatus according to the present invention includes tubular prostheses comprising an expansible tubular frame having a sealing layer formed at least partially over an exterior surface thereof. The sealing layer may be formed of any of the materials described above.
The apparatus according to the present invention further includes a fluid delivery catheter comprising a catheter body having a proximal end and a distal end. An outer balloon and an inner balloon are disposed on the catheter near its distal end. The outer balloon is positioned over the inner balloon and includes a plurality of fluid delivery ports formed over its surface. The outer balloon is connected to a first lumen within the catheter body and can receive a fluid or semi-solid sealing material therethrough. The inner balloon is connected to a second lumen within the catheter body and can receive an expansion medium therethrough. By first filling the outer balloon with the fluid or semi-solid sealing material, and thereafter expanding the inner balloon within the outer balloon, the sealing material is extruded outwardly through the fluid delivery ports in an annuler layer over the inner surface of the luminal wall. The prosthesis may then be delivered to the body lumen and expanded so that it becomes embedded in the layer of sealing material. The sealing material hardens, optionally with the application of energy conforming to the exterior of the prosthesis and providing a substantially permanent anchor and barrier to the bypass of body fluid.